textproduct: Rapid City

KEY MESSAGES

- Warm and breezy with near-critical fire weather conditions through Saturday - Pattern change Saturday night through Monday will result in showery, cooler weather with potential active/severe thunderstorms over south-central South Dakota Sunday afternoon/early evening

UPDATE

Issued at 934 PM MDT Fri May 15 2026

03z surface analysis had weak high from MT into the Dakotas with weak return flow starting across the far southwest given increasing easterly component to winds. Few radar returns have popped up over northwestern SD with a few bumps per IR satellite loop (under right entrance region of 100kt jet), so have added isolated sprinkles for late this evening. Water vapour loop has westerly flow aloft over the northern Plains with jet streak/trough starting to amplify flow over the northwest CONUS. This will be the main weather maker into early next week.

Broad strokes of current forecast in decent shape. Another warm day tomorrow as thermal ridge changes little and upper trough develops over the northern Rockies. Initial impulse ahead of it saunters into the plains with 35-45kt low level jet Saturday night over western SD. Low level theta-e advection fairly robust with weak MUCAPE developing. Showers/TS will breakout Saturday evening, moving northeast through Sunday morning. As first impulse departs, it will push a cold front through the CWA. Position of cold front Sunday afternoon/evening will determinate where moderate buoyancy/strong shear regime and resultant severe thunderstorm potential develops. SPC HREF only out to early Saturday morning right now, but some of the 00z CAMS suggest main action will be east of the CWA. Confidence in frontal position is low, however, with Saturday night convection playing a big role in how fast/slow the cold front moves through. Upper trough then approaches for Sunday/Monday with modest QG-forcing, increasing PWATs, and bands of 800-600mb frontogenesis. Good setup for beneficial rains for parts of the CWA. Latest ensemble guidance trend has been further east for heaviest QPF band, which is reflected in latest QPF forecast. Cold enough in the Black Hills for some refreshing snow up high.

DISCUSSION

(This Evening Through Friday) Issued at 1230 PM MDT Fri May 15 2026

A pattern change is still expected this weekend. For now, we are still holding on to near-critical fire weather through Saturday. Saturday night into early next week, the rain chances return to the area with cooler temps sliding in from the north.

To start the forecast, zonal flow in the upper levels will give very little change to our weather. So highs in the 70s and 80s are expected Saturday, overnight lows tonight through Saturday night will be in the 30s to 40s. Skies will be clear to mostly clear with clouds increasing from the west Saturday. And with not much moisture in the area, afternoon relative humidities will be low, at around 10 to 20%. Sustained winds will top out around 10 to 25 mph and gusts will reach near 20 to 40 mph, strongest winds in the SD plains northeast of the Black Hills. Decided to hold off on issuing a Red Flag Warning because the strongest wind speeds look to happen where relative humidity will be near 20%. And where the RH values bottom out near 10 to 15%, winds are forecast to be on the lighter side. These forecast conditions will be monitored closely and if needed, warning products will be issued.

Sunday and early next week, a passing upper level trough and surface cold front will bring some very different weather to NE WY and W SD. For starters, Saturday night into Sunday, showers and thunderstorms are likely. Some of those thunderstorms have the possibility to be strong to severe in south-central SD. The SPC has highlighted this area with a Marginal risk.

Sunday could play out to be an interesting weather day. It's looking like a surface low will develop near the NE-WY-to-Black- Hills area Sunday morning and track eastward. As it does, it will develop a cold front that will swing to the southside of the low. As the cold front slides east, thunderstorm development is possible. The timing of the cold front will highly influence where the strongest storms will be. A slower moving front will lead to more storms in western SD while a quicker moving front will lead to most of the thunderstorm action happening to the east of the CWA. For now, it's looking like a quicker moving front is the most likely scenario but uncertainty is high at this time.

As the cooler air slides into the area behind the cold front, most of the area has a decent chance of seeing rain but higher elevations of the Black Hills have a good chance of seeing accumulating snow Sunday night into Monday. At this times, upwards of 3 to 6 inches is possible. Stay tuned for updates.

For the rest of next week, PoPS diminish and temps warm back to the 60s and 70s for highs.

AVIATION

(For the 06Z TAFS Through 06Z Saturday Night) Issued At 1050 PM MDT Fri May 15 2026

Conditions will remain VFR through tonight. Gusty southerly flow will ramp up Saturday afternoon ahead of elevated storms moving through the area around 02Z Sunday. These scattered showers may have gusty and erratic outflows.

FIRE WEATHER

Issued At 1230 PM MDT Fri May 15 2026

Warm, dry, and windy conditions with receptive fuels will continue to support near-critical conditions to most of western SD through Saturday.

The gusty winds from today will weaken this evening but RH values will see poor overnight recovery. Dry and breezy weather will stick around through Saturday. That being said, as of now, it's looking like the winds will be below thresholds where RH is low enough, so decided to hold off on issuing red flag warning for now.

Cooler with shower chances early next week, leading to a break in fire weather concerns although the best chance for wetting rains will be east of the area.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.